60CM Obitsu? My favorite dollieh...
Regarding joints. I'm going to refer to an image that Parabox has. I will provide a link, but not post the image, so you will have to click on it to see the image....
60cm Obitsu Body/Joint typesGoing from left to right in this picture there are 4 combinations that illustrate pretty much all possible choices with obitsu.
1) 3-piece 'normal body'. This body is three pieces of rigid vinyl that uses the same internal skeleton as the others. the joints on this one are the ones that Misheru called 'sliding joint' because the joint pivots in two places and has a knee-cap or elbow piece that effectively covers the joint when it flexes.
2) 2 piece soft body with sliding joints. In terms of the internal skeleton, jointing, arm and leg vinyl, this is the same as (1) however, the abdomen is now a single piece made from a flexible vinyl that bends and flexes as the skeleton moves. the skeleton itself can move at the waist and just below the breast bone. So this flexible abdomen enhances the doll over and above the 3pice hard body. The joints are the same sliding joints as before. You can also make this doll using the hard bust piece (as shown in the picture, or you can use a soft bust piece designed to fit the soft abdomen. At Parabox this is known as the Soft Body A.
3) This is the standard ball-joint body. the abdomen and chest are both made of soft vinyl. the internal skeleton of the body is the same as the others, but the joints and limbs are different. the leg and arm vinyl of the ball joint dolls is not interchangeable with the leg/arm vinyl on the sliding joint bodies. The joint construction is quite different which means that the vinyl itself is shaped differently to accommodate the ball joint instead of the sliding joint mechanism. These joints look more natural when flexed when compared to the sliding joints. They can also handle considerable range via a special slide mechanism that allows one part of the joint to slide out of the other (almost dislocating) for extreme range of motion.
4) this final example is a hybrid of the slimline body normally sold with the ball jointed limbs and the slightly larger limbs of the sliding joint mechanism. The internal skeleton of the body remains the same across all of the versions with only the limbs and their joints changing.
You can create other combinations, such as the soft body A abdomen, with a larger bust piece on a body using the ball-joints. Aesthetically I prefer the look of the ball joints, but the sliding joints have their charm too, and once your lady is dressed and her personality has solidified it won't matter what kind of joints she has, you generally won't see them anyway.
Here is a page from parabox with some more comparisons of the jointing and body styles.
http://parabox.jp/obitsu/60-4shu.htmland here is another picture showing the internal skeleton (including limbs) of the sliding joints vs the ball joints.
Sliding vs ball joints.I have several ladies using the standard slim ball-joint body, I have one lady who uses the sliding joints and has a soft abdomen and large (parabox) optional bust, and another lady who uses the ball-joints but uses the soft abdomen and a larger bust piece. I've found that the larger bust pieces are generally a better size match for the soft body abdomen rather than the slim abdomen that comes with the ball joint bodies.